A compressor unit of this type is known, for example, from WO-A-94/29597 and EP-A 1 074 746.
In the compressor unit which is known from WO-A 94/29597, a compressor impeller is arranged on both sides of the electric motor. The rotor shaft is mounted in two radial magnetic bearings, which are each arranged between the electric motor and a compressor impeller, and an axial magnetic bearing, which is likewise arranged between the electric motor and one of the compressor impellers.
In the compressor unit which is known from EP-A 1 074 746, in particular FIG. 2, the compressor impellers are arranged on one side of the electric motor. The rotor shaft comprises two parts which are connected to one another by means of a coupling. The rotor shaft is mounted in three radial magnetic bearings which are arranged at both ends of the rotor shaft and between the electric motor and the centrifugal compressor, and one axial magnetic bearing, which is arranged between the electric motor and the centrifugal compressor.